In accordance to Rome IV Criteria irritable bowel syndrome (IBS) is classified into four subtypes: IBS with predominant constipation (IBS-C), IBS with predominant diarrhea (IBS-D), with mixed bowel habits (IBS-M) or IBS, unsubtyped. Some authors distinguish a post-infectious subtype of IBS, in which an acute episode of infectious gastroenteritis is a trigger of the disorder. In all the other cases, mostly psycho-emotional stress is the trigger factor, with this variant being defined as stress-associated subtype of IBS.
Aim: to study the peculiarities of the formation and course of IBS in children, depending on the trigger factor. A total of 54 patients aged 6-12 years with a verified diagnosis of IBS according to Rome criteria IV have been examined. The trigger factor of the onset of IBS was established by the interrogation of patients and their parents. The levels of trait anxiety and somatization were assessed by Children's Form of the Manifest Anxiety Scale (CMAS) questionnaire and Somatoform Symptom Screening (SOMS) test respectively. The Catechol-O-methyltransferase (COMT) gene val158met polymorphism was estimated by the polymerase chain reaction. Enzyme immunoassay Ridascreen Calprotectin (R-Biopharm AG, Germany) was used for the quantitative determination of calprotectin in stool samples.
Results. We have diagnosed post-infectious subtype of IBS in 30 children. In this group we have found significantly higher concentration of fecal calprotectin (60.0 (35.6; 129.0) vs 31.2 (21.1; 58.7 mkg/g of feces)), which is consistent with pathogenesis of this subtype of IBS. On the contrary, we have discovered that psycho-emotional stress was the trigger factor of the onset of IBS in 22 patients (stress-associated subtype of IBS). Children with stress-associated IBS had higher levels of trait anxiety (25.1±5.7 vs. 18.7±6.4) and somatization (11.1 ± 4.0 vs. 8.6 ± 3.1) in comparison to patients with post-infectious subtype of the disorder. Furthermore, the analysis of the COMT gene polymorphism revealed, that almost the half patients (48%) with stress-associated IBS had 472 AA (Met/Met) genotype. Met/Met carriers have genetically determined low enzymatic activity of COMT, which may lead to decreased elimination of catecholamines and is associated with chronic stress. In contrast, only 31% of children with post-infectious subtype of IBS were found to have 472 AA (Met/Met) genotype.
Conclusions. Our study suggests that not only predominant bowel habit, but also trigger factor in the development of IBS determine the heterogeneity of the disorder. This approach may be used for classification of IBS in children, as it dictates treatment strategy.